With Manic/Depressive is there a correlation between the two phases?

What I mean is, can it be a mild depression after a hightened manic phase or is a hightened manic phase always followed by a deeper depressive one or is there no relationship? Is it always a crash and burn scenario or can you come down gently?
And, is it normal for a person in the manic phase to go without sleep for extended periods of time?
What about increased drug and alcohol use? Is there cause and effect here? Is the manic further enhanced by them or does the manic phase drive someone to them?
Will emotional trauma bring on the manic phase?
All advice, particularly from those who might have experienced this welcome.